Merge branch 'release/0.5' into develop
Adds the database exporter. Use it like this:

dbexp \
	-x ticket_corner_id,created_by_api_key_id,communicated_to_ticket_corner,current_season_statistics,privacy_rankings_user_name,address.federal_state,race_profile.current_ski,race_profile.current_snowboard,current_fitness_profile.user_id \
	-i address,newsfeed,current_fitness_profile,race_profile,address.country,security_info_id \
	skiline@localhost/skiline/user/version\>10000
Better checks of include/exclude columns. Better exception handling.
Fixes last failing test case. Renames dbexp to dbexport.
Fixes issues with some datatypes (bool, datetime).
Allows for multiple filters (& is the separator).
Adds a graph from the database.
Better visualisation of graph.
Adds columns to output, too.
Refactors code.
Adds recursive graph creation (using a breadth first search algorithm). Adds graphviz output format. Adds an option to additionally display non foreign key columns. Removes deprecated debug messages. Adds a new operator not equals (!=).
Uses deque as data structure.
Simplifies writers.
Adds an error recovery format for the writer.
Fixes missing re import. Updates README.md.
Adds the usage of dbnav, dbgraph and dbexport.
Adds a table of contents
Updates table of contents.
Fixes include and exclude with breadth first search.
Refactors tests.